A magnitude 5.1 earthquake struck the Gulf of Gemlik south of Istanbul on Monday without causing major damage or casualties, Turkish authorities said.
According to the Turkish civil protection agency AFAD, the epicenter of the earthquake is in the Sea of Marmara off the coast of Gemlik, almost 120 km south of Istanbul and near Bursa.
AFP journalists felt the tremors in the Asian and European parts of Istanbul, while residents poured into the streets in Bursa fearing a building collapse, according to images released by Turkish media.
With a population of more than 15 million, Istanbul is the largest city in Turkey facing fears of a major earthquake due to its proximity to the North Anatolian Fault, one of the most active in the world.
A magnitude 7.6 earthquake struck the city in 1999, killing more than 17,000 people.
Two severe earthquakes struck southeastern Turkey in February, killing more than 50,000 people and devastating around ten cities in the region.